1. Field of the Invention
The present invention relates to a flow channel switching valve for use in, for example, an auto-sampler that introduces a sample to an analysis flow channel of a liquid chromatograph.
2. Description of the Related Art
As an example, in an auto-sampler that introduces a sample to an analysis flow channel of a liquid chromatograph, after the sample is taken into a sample loop from a sample container, the sample loop is connected to an upstream side of a separation column in the analysis flow channel by switching of a flow channel switching valve, which allows the sample in the sample loop to be transported to a separation column side by a mobile phase flowing in the analysis flow channel.
As the flow channel switching valve for use in the liquid chromatograph, a rotary type switching valve is common. The rotary type switching valve switches a connected flow channel by rotating a rotor (rotary part) (e.g., refer to Unexamined Japanese Patent Publication No. 2008-215494).
In the rotary type switching valve, a plurality of connection ports for connecting flow channel piping are provided in an upper portion of a housing, and a rotor and a stator (stationary part) are contained inside the housing. In the housing, the upper portion (hereinafter, a housing top) of the housing provided with the connection ports is detachable from a body of the housing (hereinafter, a housing body), and the exchange of parts such as the rotor, the stator, and the like is performed in a state where the housing top is detached from the housing body. The rotor and the stator are in contact with each other in a state where planes thereof keep liquid tightness with each other, and the stator is fixed by a pin or the like so as not to rotate with respect to a housing side. The connection ports communicate with the rotor through flow channels provided in the housing and holes of the stator. A groove forming a flow channel connecting between the connection ports is provided in a surface on a stator side of the rotor, and driving and rotating the rotor while sliding on the stator changes a position of the groove, thereby switching connection between the connection ports. There is also a rotary type switching valve in which a stator is integrated with the housing top.
The rotor is held by a forefront portion of a rotor drive shaft extending to a housing top side from a housing body side. A rotational mechanism that rotates the rotor drive shaft, such as a motor and the like, is provided on a base end side of the rotor drive shaft, and rotating the rotor drive shaft allows the rotor to be rotated. In order to keep the liquid tightness between the rotor and the stator, generally, a spring extendable in an axial direction of the rotor drive shaft is contained in a compressed state inside the housing body, and biases the rotor drive shaft to the housing top side by an elastic force of the spring, which increases a contact pressure between the rotor and the stator.
When inspection of an inside of the valve or exchange of consumable stores such as the rotor and the like are performed, the housing top needs to be detached from the housing body. The housing top is attached to the housing body by a plurality of bolts, and when the bolts are loosened, the spring pushing the rotor drive shaft to the housing top side tries to return to a natural length, thereby largely lifting the rotor drive shaft, and at this time, there may be posed problems that a contact pressure applied to the rotor is largely biased, thereby damaging the rotor, and the like. Thus, the respective bolts need to be loosened evenly little by little (e.g., by 90° or the like), and the detachment of the housing top needs to be performed carefully. Similarly, when the housing top is attached to the housing body, the bolts need to be fastened carefully to make the contact pressure on the rotor even.